Not obligate; optional, discretionary or elective.
That grants permission or power to do something.
Able to perform a particular life function, or to live generally, in more than one way.
Of or relating to faculty, especially to mental faculty.
At which a given function is positive.
Having the authority or capability to make a selection.
choosy, fussy or discriminating when selecting.
Of or relating to the process of selection.
Of or relating to natural selection.
Of or relating to the social work approach called selectivity.